Sensing sub-assembly and method of operating a hydraulic fracturing system

ABSTRACT

A sensing sub-assembly for use with a drilling assembly that includes a cylindrical body including an internal flow channel extending therethrough. The internal flow channel is configured to channel a first fluid therethrough. A recessed cavity is also defined therein. The recessed cavity is coupled in flow communication with an ambient environment exterior of the cylindrical body, and a second fluid flows within the ambient environment. The recessed cavity is configured to receive a continuous stream of the second fluid therethrough. At least one sensor is coupled to the cylindrical body, and the at least one sensor is configured to determine characteristics of the second fluid in the continuous stream that flows through the recessed cavity.

BACKGROUND

The present disclosure relates generally to wellbore drilling and formation evaluation and, more specifically, to a Logging-While-Drilling or Measurement-While-Drilling sensing system for downhole hydrocarbon and gas species detection when forming a wellbore in a subterranean rock formation.

Hydraulic fracturing, commonly known as fracking, is a technique used to release petroleum, natural gas, and other hydrocarbon-based substances for extraction from underground reservoir rock formations, especially for unconventional reservoirs. The technique includes drilling a wellbore into the rock formations, and pumping a treatment fluid into the wellbore, which causes fractures to form in the rock formations and allows for the release of trapped substances produced from these subterranean natural reservoirs. At least some known unconventional subterranean wells are evenly fractured along the length of the wellbore. However, typically less than 50 percent of the fractures formed in the rock formations contribute to hydrocarbon extraction and production for the well. As such, hydrocarbon extraction from the well is limited, and significant cost and effort is expended for completing non-producing fractures in the wellbore.

BRIEF DESCRIPTION

In one aspect, a sensing sub-assembly for use with a drilling assembly is provided. The sensing sub-assembly includes a cylindrical body including an internal flow channel extending therethrough. The internal flow channel is configured to channel a first fluid therethrough. A recessed cavity is also defined therein. The recessed cavity is coupled in flow communication with an ambient environment exterior of the cylindrical body, and a second fluid flows within the ambient environment. The recessed cavity is configured to receive a continuous stream of the second fluid therethrough. At least one sensor is coupled to the cylindrical body, and the at least one sensor is configured to determine characteristics of the second fluid in the continuous stream that flows through the recessed cavity.

In another aspect, a method of operating a hydraulic fracturing system is provided. The method includes advancing a drilling assembly within a subterranean rock formation. The drilling assembly is configured to discharge a first fluid into the subterranean rock formation, and a second fluid flows past an exterior of the drilling assembly. The method further includes channeling a continuous stream of the second fluid through at least a portion of the drilling assembly, and determining characteristics of the second fluid in the continuous stream channeled through the drilling assembly.

DRAWINGS

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic illustration of an exemplary hydraulic fracturing system, including a drilling assembly, that may be used to form a wellbore;

FIG. 2 is a perspective view of an exemplary sensing sub-assembly that may be used in the drilling assembly shown in FIG. 1;

FIG. 3 is a perspective view of an exemplary sensing hub that may be used with the sensing sub-assembly shown in FIG. 2;

FIG. 4 is a schematic cross-sectional view of the sensing hub shown in FIG. 3, taken along Line 4-4;

FIG. 5 is a perspective front view of an alternative sensing hub that may be used with the sensing sub-assembly shown in FIG. 2;

FIG. 6 is a perspective front view of a further alternative sensing hub that may be used with the sensing sub-assembly shown in FIG. 2; and

FIG. 7 is a perspective front view of a further alternative sensing hub that may be used with the sensing sub-assembly shown in FIG. 2.

Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.

DETAILED DESCRIPTION

In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings.

The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

Furthermore, as used herein, the term “real-time” refers to at least one of the time of occurrence of the associated events, the time of measurement and collection of predetermined data, the time to process the data, and the time of a system response to the events and the environment. In the embodiments described herein, these activities and events occur substantially instantaneously.

Embodiments of the present disclosure relate to a sensing system for downhole hydrocarbon and gas species detection when forming a wellbore in a subterranean rock formation. The sensing system is implemented as a standalone evaluation tool or installed as part of a wellbore drilling assembly. The sensing system determines characteristics of a first fluid discharged from the drilling assembly, and a second fluid that flows past the drilling assembly in the wellbore. More specifically, the sensing system includes a recessed cavity that receives a continuous stream of the second fluid, separate from the main flow of the second fluid. At least one sensor is positioned within the recessed cavity to facilitate protecting the sensor from the caustic and abrasive wellbore environment. The sensor is used to determine characteristics of the fluid, and the characteristics are analyzed to determine the hydrocarbon content of the fluid. As such, the analysis results are used to identify potentially promising fracture initiation zones within the wellbore such that efficient and cost effective completion planning can be implemented.

For example, downhole hydrocarbon and gas species detection while drilling can identify zones of high permeability, such as open natural fractures, clusters of closed but unsealed natural fractures, larger pores and other formation features where hydrocarbons are stored. The analysis results can be used to identify the most promising fracture initiation points or zones, and the information can be used for completion planning, especially for unconventional reservoirs. In addition, the analysis results can be used to identify poor zones (no gas show), which facilitates reducing the time and effort of perforating and stimulating the poor zones. Another potential application is for geosteering assistance, wherein the real time gas show/species information is used to adjust the borehole position (e.g., inclination and azimuth angles) while drilling, such that a well having increased production can be formed. Finally, the sensing can also provide kick detection to facilitate providing real-time alerts of gas flow potential for safety and environmental considerations, thereby reducing the risk of system failure.

FIG. 1 is a schematic illustration of an exemplary hydraulic fracturing system 10. Hydraulic fracturing system 10 includes a drilling assembly 100 that may be used to form a wellbore 102 in a subterranean rock formation 104. In the exemplary embodiment, drilling assembly 100 includes a plurality of sub-assemblies and a drill bit 106. More specifically, the plurality of sub-assemblies include a measurement-while-drilling or logging-while-drilling sub-assembly 108, a sensing sub-assembly 110, a mud motor 112, and bent housing or rotary steerable system sub-assemblies 114 coupled together in series. Drilling assembly 100 includes any arrangement of sub-assemblies that enables drilling assembly 100 to function as described herein.

FIG. 2 is a perspective view of sensing sub-assembly 110 that may be used in drilling assembly 100 (shown in FIG. 1. In the exemplary embodiment, sensing sub-assembly 110 includes a first outer casing 116, a second outer casing 118, and a sensing hub 120 coupled therebetween. First outer casing 116 includes a first end 122 and a second end 124, and second outer casing 118 includes a first end 126 and a second end 128. First end 122, second end 124, first end 126, and second end 128 each include a threaded connection for coupling sensing sub-assembly 110 to one or more of the plurality of sub-assemblies of drilling assembly 100, and for coupling first outer casing 116 and second outer casing 118 to sensing hub 120.

FIG. 3 is a perspective view of sensing hub 120 that may be used with sensing sub-assembly 110 (shown in FIG. 2), and FIG. 4 is a schematic cross-sectional view of sensing hub 120, taken along Line 4-4 (shown in FIG. 3). In the exemplary embodiment, sensing hub 120 includes a cylindrical body 130 including a first end 132 and a second end 134. First end 132 and second end 134 each include a threaded connection for coupling to first outer casing 116 and second outer casing 118 (both shown in FIG. 3), as described above. In addition, cylindrical body 130 includes an internal flow channel 136 extending therethrough that channels high pressure fluid during operation of drilling assembly 100, as will be described in more detail below.

Cylindrical body 130 further includes a recessed cavity 138 defined therein. Recessed cavity 138 is either at least partially obstructed from or fully exposed to an ambient environment 140 exterior of cylindrical body 130, as will be explained in more detail below. As shown in FIG. 4, recessed cavity 138 is at least partially obstructed from ambient environment 140. More specifically, cylindrical body 130 further includes a flow inlet 142 and a flow outlet 144 defined therein, such that an outer portion 146 of cylindrical body 130 is positioned between recessed cavity 138 and ambient environment 140. In addition, recessed cavity 138 is extends longitudinally parallel with internal flow channel 136. Alternatively, recessed cavity 138 extends helically within cylindrical body 130 to increase the flexibility for sensor arrangement within recessed cavity 138.

During operation of drilling assembly 100 (shown in FIG. 1), a first fluid 148 is channeled through internal flow channel 136, and is discharged from drilling assembly 100, and a second fluid 150 backflows within wellbore 102 (shown in FIG. 1) past drilling assembly 100. First fluid 148 flows at a greater pressure than second fluid 150, and second fluid 150 includes a portion of first fluid 148 and constituents of subterranean rock formation 104. Referring to FIG. 4, in one embodiment, recessed cavity 138 receives a continuous stream of second fluid 150 therethrough. More specifically, flow inlet 142 channels the continuous stream of second fluid 150 into recessed cavity 138, and flow outlet 144 discharges the continuous stream of second fluid 150 from recessed cavity 138. As such, second fluid 150 is channeled through recessed cavity 138 for further analysis either continuously or at predetermined intervals, as will be explained in more detail below.

In the exemplary embodiment, sensing sub-assembly 110 includes at least one sensor coupled to cylindrical body 130. As will be described in further detail below, the at least one sensor determines characteristics of first fluid 148 and second fluid 150, and the data obtained from the at least one sensor is analyzed to determine the hydrocarbon content of second fluid 150. Exemplary characteristics determined by the at least one sensor includes, but is not limited to, density, viscosity, electromagnetic characteristics, acoustic impedance, sound speed, sound attenuation, and attenuation coefficient. Exemplary sensors include, but are not limited to, an ultrasound sensor, and an acoustic sensor, such as an acoustic transducer. Alternatively, any sensors for determining characteristics of first fluid 148 and second fluid 150 may be utilized that enables sensing sub-assembly 110 to function as described herein.

In one embodiment, referring to FIG. 4, the at least one sensor includes a first pair 152 of sensors, including a first sensor 154 and a second sensor 156. First sensor 154 is positioned for determining characteristics of first fluid 148 within internal flow channel 136, and second sensor 156 is positioned for determining characteristics of second fluid 150 within recessed cavity 138. First pair 152 of sensors operate at the same frequency, such that the data obtained from first sensor 154 and second sensor 156 are comparable relative to each other for determining the hydrocarbon content in second fluid 150, as will be explained in more detail below. In one embodiment, first sensor 154 and second sensor 156 are wide band transducers that operate at a frequency defined within a range between and including about 100 kilohertz (khz) and 20 megahertz (Mhz).

Alternatively, the at least one sensor includes first pair 152 of sensors and a second pair 158 of sensors, including a third sensor 160 and a fourth sensor 162. Similar to first pair 152 of sensors, third sensor 160 is positioned for determining characteristics of first fluid 148 within internal flow channel 136, and fourth sensor 162 is positioned for determining characteristics of second fluid 150 within recessed cavity 138. In addition, first pair 152 of sensors operate at the same first frequency, and second pair 158 of sensors operate at the same second frequency. In the exemplary embodiment, the operating frequencies of first pair 152 and second pair 158 are defined within a sub-range of the operating frequency of the wide band transducer described above (i.e., sub-ranges spanning a portion of the range defined between and including about 100 kilohertz khz and about 20 megahertz Mhz) that collectively span a wide frequency range. As such, the data obtained from third sensor 160 and fourth sensor 162 are comparable relative to each other for determining the hydrocarbon content in second fluid 150. In addition, operating first pair 152 of sensors and second pair 158 of sensors at more narrowly defined frequency sub-ranges facilitates increasing the frequency resolution of the transmitted and received signals.

In some embodiments, the at least one sensor further includes a third pair 164 of sensors, including a fifth sensor 166 and a sixth sensor 168. Fifth sensor 166 and sixth sensor 168 are positioned for determining characteristics of second fluid 150 within recessed cavity 138. More specifically, one of fifth sensor 166 and sixth sensor 168 is an emitter, and the other sensor is a receiver. In addition, recessed cavity 138 has a length L and a width W shorter than length L. Fifth sensor 166 and sixth sensor 168 are longitudinally spaced from each other within recessed cavity 138 relative to length L. Longitudinally spacing fifth sensor 166 and sixth sensor 168 from each other facilitates increasing the distance therebetween, such that the distance is not limited by the diameter of cylindrical body 130. Moreover, in one embodiment, fifth sensor 166 and sixth sensor 168 are low frequency transducers that operate at a frequency defined within a range between and including about 10 kHz and about 20 kHz. When compared to higher frequency transducers, the sensor readings obtained from third pair 164 of sensors are less likely to be scattered by gas bubbles contained in second fluid 150, for example. As such, operating third pair 164 of sensors at a low frequency range facilitates increasing the amount of useful data obtained for later analysis and evaluation to determine the hydrocarbon content of second fluid 150.

FIG. 5 is a perspective front view of an alternative sensing hub 170 that may be used with sensing sub-assembly 110 (shown in FIG. 2). As described above, cylindrical body 130 includes a recessed cavity that is either at least partially obstructed from or fully exposed to ambient environment 140 exterior of cylindrical body 130. In the exemplary embodiment, sensing hub 170 includes a recessed cavity 172 fully exposed to ambient environment 140. More specifically, recessed cavity 172 is defined by a circumferential indent 174 extending about cylindrical body 130. As such, second fluid 150 freely flows within recessed cavity 172 during operation of drilling assembly 100 (shown in FIG. 1).

In the exemplary embodiment, circumferential indent 174 defines a first mounting surface 176 and a second mounting surface 178 spaced longitudinally from, and oriented to face each other. In addition, the at least one sensor includes at least one pair 180 of sensors spaced longitudinally from each other, and each sensor in pair 180 is coupled to either first mounting surface 176 or second mounting surface 178. Longitudinally spacing each sensor in pair 180 from each other facilitates increasing the distance therebetween, such that the distance is not limited by the diameter of cylindrical body 130. As described above, the distance between a transmitter and a receiver of a sensor pair is selected based on an operating frequency of the sensor pair.

FIG. 6 is a perspective front view of a further alternative sensing hub 182 that may be used with sensing sub-assembly 110 (shown in FIG. 2), and FIG. 7 is a perspective front view of a further alternative sensing hub 184 that may be used with sensing sub-assembly 110. In the exemplary embodiment, sensing hub 182 and sensing hub 184 both include a central body 186 and a plurality of longitudinal members 188 arranged circumferentially within circumferential indent 174. More specifically, the plurality of longitudinal members 188 extend between first mounting surface 176 and second mounting surface 178 such that mechanical robustness of sensing hub 182 and sensing hub 184 are improved without substantially interfering with the fluid dynamics of second fluid 150 channeled within recessed cavity 172.

Referring to FIG. 6, the plurality of longitudinal members 188 are positioned at an outer edge 190 of circumferential indent 174. As such, second fluid 150 is capable of flowing not only longitudinally, but also helically within recessed cavity 172. Referring to FIG. 7, the plurality of longitudinal members 188 extend radially from central body 186 towards outer edge 190. As such, recessed cavity 172 is partitioned into a plurality of predefined sectors 192, and a pair 180 of sensors is positioned within each sector 192. More specifically, in each of sensing hub 182 and sensing hub 184, the at least one sensor is circumferentially offset from adjacent pairs of longitudinal members 188 such that second fluid 150 is substantially unobstructed from flowing within recessed cavity 172.

The systems and assemblies described herein facilitate providing at least semi-continuous hydrocarbon and gas species detection feedback when drilling unconventional subterranean wells. More specifically, the drilling assembly facilitates analyzing fluid used in the drilling process in a fast and efficient manner. The data obtained from the analysis of the fluid samples can then be used to determine zones within a wellbore that have either a low likelihood or a high likelihood of having a high hydrocarbon content. As such, the zones having a high hydrocarbon content are identified, and fracture completion planning resulting in improved well production is determined.

An exemplary technical effect of the systems and assemblies described herein includes at least one of: (a) providing real-time and continuous hydrocarbon and gas species detection feedback when forming a well in a subterranean rock formation; (b) identifying potentially promising fracture initiation zones within a wellbore; (c) improving hydrocarbon production for wells; (d) providing geosteering assistance for the drilling assembly; and (e) providing kick detection for real-time gas flow potential safety alerts.

Exemplary embodiments of a drilling assembly and related components are described above in detail. The drilling assembly is not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the configuration of components described herein may also be used in combination with other processes, and is not limited to practice with only drilling and sensing assemblies and related methods as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many applications where analyzing one or more fluids is desired.

Although specific features of various embodiments of the present disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of embodiments of the present disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

This written description uses examples to disclose the embodiments of the present disclosure, including the best mode, and also to enable any person skilled in the art to practice embodiments of the present disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the embodiments described herein is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A sensing sub-assembly for use with a drilling assembly, said sensing sub-assembly comprising: a cylindrical body comprising: an internal flow channel extending therethrough, said internal flow channel configured to channel a first fluid therethrough; and a recessed cavity defined therein, said recessed cavity coupled in flow communication with an ambient environment exterior of said cylindrical body, wherein a second fluid flows within the ambient environment, and said recessed cavity is configured to receive a continuous stream of the second fluid therethrough; and at least one sensor coupled to said cylindrical body, said at least one sensor configured to determine characteristics of the second fluid in the continuous stream that flows through said recessed cavity.
 2. The sensing sub-assembly in accordance with claim 1, wherein said cylindrical body further comprises a flow inlet and a flow outlet defined therein, wherein said flow inlet is configured to channel the continuous stream of the second fluid into said recessed cavity, and said flow outlet is configured to discharge the continuous stream of the second fluid from said recessed cavity.
 3. The sensing sub-assembly in accordance with claim 1, wherein said at least one sensor comprises a first pair of sensors comprising a first sensor and a second sensor, said first sensor positioned for determining characteristics of the first fluid within said internal flow channel, and said second sensor positioned for determining characteristics of the second fluid within said recessed cavity.
 4. The sensing sub-assembly in accordance with claim 3, wherein said at least one sensor comprises a second pair of sensors, said first pair of sensors configured to operate at a different frequency than said second pair of sensors.
 5. The sensing sub-assembly in accordance with claim 4, wherein said second pair of sensors comprises a third sensor and a fourth sensor, said third sensor positioned for determining characteristics of the first fluid within said internal flow channel, and said fourth sensor positioned for determining characteristics of the second fluid within said recessed cavity.
 6. The sensing sub-assembly in accordance with claim 4, wherein said second pair of sensors comprises a fifth sensor and a sixth sensor, said fifth sensor and said sixth sensor longitudinally spaced from each other within said recessed cavity.
 7. The sensing sub-assembly in accordance with claim 1, wherein said recessed cavity is defined by a circumferential indent extending about said cylindrical body such that said recessed cavity is exposed to the ambient environment.
 8. The sensing sub-assembly in accordance with claim 7, wherein said cylindrical body further comprises a plurality of longitudinal members arranged circumferentially within said circumferential indent.
 9. The sensing sub-assembly in accordance with claim 8, wherein said at least one sensor is circumferentially offset from adjacent pairs of longitudinal members of said plurality of longitudinal members.
 10. The sensing sub-assembly in accordance with claim 1, wherein said at least one sensor comprises at least one of an ultrasound sensor and an acoustic sensor.
 11. A method of operating a hydraulic fracturing system, said method comprising: advancing a drilling assembly within a subterranean rock formation, wherein the drilling assembly is configured to discharge a first fluid into the subterranean rock formation, and wherein a second fluid flows past an exterior of the drilling assembly; channeling a continuous stream of the second fluid through at least a portion of the drilling assembly; and determining characteristics of the second fluid in the continuous stream channeled through the drilling assembly.
 12. The method in accordance with claim 11 further comprising identifying fracture initiation locations within the subterranean rock formation based on the characteristics of the second fluid in the continuous stream.
 13. The method in accordance with claim 12, wherein identifying fracture initiation locations comprises: determining, with a first sensor of a first pair of sensors, characteristics of the first fluid; determining, with a second sensor of the first pair of sensors, characteristics of the second fluid in the continuous stream; and comparing the characteristics of the first fluid to the characteristics of the second fluid in the continuous stream.
 14. The method in accordance with claim 13 further comprising operating the first sensor and the second sensor at the same frequency.
 15. The method in accordance with claim 14, wherein operating the first sensor and the second sensor comprises operating the first sensor and the second sensor at a frequency defined within a range between and including about 100 kilohertz and 20 megahertz.
 16. The method in accordance with claim 13 further comprising determining, with a second pair of sensors, characteristics of the second fluid in the continuous stream, wherein the first pair of sensors are configured to operate at a first frequency and the second pair of sensors are configured to operate at a second frequency different from the first frequency.
 17. The method in accordance with claim 16 further comprising operating the second pair of sensors at the second frequency defined within a range between and including about 10 kilohertz and about 20 kilohertz.
 18. The method in accordance with claim 13 further comprising: determining, with a third sensor of a third pair of sensors, characteristics of the first fluid; and determining, with a fourth sensor of the third pair of sensors, characteristics of the second fluid in the continuous stream, wherein the first pair of sensors are configured to operate at a first frequency and the third pair of sensors are configured to operate at a third frequency different from the first frequency.
 19. The method in accordance with claim 11, wherein determining characteristics of the second fluid comprises determining characteristics of the second fluid with at least one of an ultrasound signal and an acoustic signal.
 20. The method in accordance with claim 19, wherein determining characteristics of the second fluid comprises determining a hydrocarbon content of the second fluid based on changes in sound speed of the at least one of the ultrasound signal and the acoustic signal through the second fluid. 